Amplifying apparatus



' Dec. 9, 1947. I A c, DEHMEL 2,432,142

AMPLIFYING APPARATUS ori inal Filed July 13. 1944 INVENTOR.

RICHARD CLDEHMEL Patented Dec. 9, 1947 UNITED STATES PATENT O F Fl CE Original application July v13, 1944, Serial No. 544,714. Divided and this application April 25,

1945,.Serial No. 590,195

3 Claims. 1 This invention relates .to amplifying pparatus and particularly to apparatus for amplifying a variable potential and producing a plurality of control potentials.

A principal object of this invention'isto ,pro- I vide an improved amplifying apparatus for amplifying a variable potential and producing a pair of control potentials, the parameters of which have a definite relationship to those. of .said variable potential.

A further object of this inventionis to provide an improved amplifying apparatus of theabove character wherein the instantaneous values of the control potentials are of opposite polarity,

This application is a division of my 'co-pending thereof is a diagrammatic View showing an arran'gement of circuit connections "and elements comprising one embodiment of the present-invention in a-specific application thereof.

In the particular arrangement shown 'an integrating device is made responsive to a variable potential by means including amplifying apparatus embodying the present invention. In general, the integrating device comprises a -register ing element actuated by a rotatable shaft which is moved in one direction in response to a positive input potential and'ln the other direction in response to a negative potential, the'velocityorrate of'movement of the shaft in either direction'being directly proportional to the input voltage. Apair of thermionic tubes are so arrangedas to amplify the input voltage and transmit it to the control grids of a pair of gas-discharge tubes such as a pair of thyratron tubes which are connected to the respective thermionic tubes in such a waythat one gas-discharge tube is actuated by :a positive input voltage, while the other is actuatedby a negative voltage. The discharge of one tube is employedto operate a mechanical device for moving the indicating member, 'suchas the rotatable :shaft referred to, in one direction, while'the. d scharge of the other tube operates a mechanism for rotating the shaft in the other direction. "The :rate of..rotation imparted to the shaft is proportional to the input voltage and the direction of rotation determined by whether the potential is :to a condenser C through an impedance suchas a resistance R, the'values of 'thec'ondenser and theresistance being-so chosenthat thecondenser is charged at a predetermined desired rate to produce a certain potential e at the junction 3 where the condenser C and conductor I are connected.

The junction 3 is connected to the grids-4 'and 5, respectively, of two thermionic tubes 6 and I to amplify the input voltage changes and transmit such amplified changes to junctionsB and 9, respectively. Consequently, the voltage changes at the junctions 8 and '9 are amplificationsof the voltage variations across the condenser C, and the connections to the thermionic tubes "6 and! are such that the potential at the junction 8 is opposite'to the potential at the junction "9. For this purpose, as Well as to provide eircuitstab'ility, the thermionic valves 6 and l are preferably twin "tri'ode tubes having cathodes Ill and H, respectively, each formed by a, single cathode element,

*or, as illustrated, by interconnected separate elements. The cathode of each tube is preferably connected to a low impedance source l2 of con stant negative potential through high ohmic resistances i3 and M, respectively. The anodes 125 and 16 of the thermionic valves are energized 2. preferably low impedancesource l "i -of constant positive potential. The respective grids l8 and ill are grounded, while the remaining anodes .2!) and :21, respectively, are energized through plate impedances and 2.3, respectively, by a preferably low impedance source 23" of constant positive potential. Additional impedances 2 1 and '25, respectively, which are energized by the constant negative potential source 1'2 are provided for the purpose of bringing the mean potential of the junctions 8 andii to approximately ground potential fora purpose hereinafter described. Obviously, the tubes have conventional filaments connected to any suitable source'o'f potential.

The amplified voltage variations of the dune- 'tionst and B may be employed for operating a "movable indicating member such, for example, as

"1y. The mean potential of the junctions send 9 is controlled through a Vernier control-provided by potentiometers '28 and 29- and it will be apparcut, as hereinafter described, thatthe circui-tcon- 'nect'ions change the potentials of the junctions 8 and "9 in an amount proportional to changesin the "potential eat junction 3, in the following manner.

A potential ,e on grid 4 of thermionic tube 6 "varies-the space current to the anode 20in a well known manner. If the potential eincreasesposi- 'tively,.the anode current to the-plate 52D .rises.

60 This causes an increased voltage drop across the impedance 22 which may be a resistance. Accordingly, the potential at the junction 38 connecting the impedance to the plate becomes negative with respect to its mean value. On the other hand, the accompanying positive increase in the potential on the grid 5 of the thermionic tube 1 produces a rise of the potential at the junction 9 in the following manner. A positive increase in the potential on the grid 5 increases the space current from the source l2 through the cathode resistor l4 and from the cathode l I to the anode [6, this current flow bein aided by the source I! of the potential. The resulting increased cathode current produces an increase in the voltage drop across the cathode resistor 14 and, hence, increases the potential of the cathode H with respect to ground and therefore with respect to the grid l9. This is the equivalent of the grid l9 becoming more negative with respect to the cathode H and thus reducing the space current to the anode 2| and through the impedance 23, which also may be a resistance similar to the resistance 22. This decreased current results in a lower voltage drop across the impedance 23 and, hence, a rise in potential at the junction 31 between the impedance and the anode 2|. Consequently, the junction 9 rises above its mean value of potential.

The junctions 8 and 8 are respectively connected to the grids 32 and 33 of the thyratron or other gas-discharge valves 26 and 21. A source 34 of alternating current is connected to the anode 35 of the tube 27 through a winding 36 and to the anode 3?! of the tube 25 through a, winding 38. The winding 35 is adapted to actuate a bell crank lever 39 havin one arm in position to operate a spring pressed pawl 4i cooperating with a ratchet 42 for rotating the shaft 43 in one direction. Similarly, the winding 38 actuates a bell crank lever 44 having an arm arranged to operate a spring pressed pawl 45 to rotate a ratchet 46 for rotating the shaft 43 in the opposite direction. A movable armature 41 connected over a lead 48 to the junction 3 and condenser C is arranged to close a ground connection 49 to discharge the condenser and thereby restore the circuit to its initial condition in readiness to repeat the cycle of operations as hereinafter described. Similarly, an armature 5| connected over a lead 52 with the junction 3 and condenser C is adapted to be actuated by the windin 38 to close a grounded contact 53 and discharge the condenser C upon actuation of the pawl and ratchet 45 and 46.

As is well known, a grid-controlled gas-discharge rectifier passes no anode current until i the potential of the grid has been increased in a positive direction above a critical negative value. Accordingly, if the grids 32 and 33 of the thyratron or similar valves are maintained at a mean negative value by adjustment of the respective potentiometers 28 and 29, the thyratron valves 28 and 21 will not discharge until the potential e at the junction 3 has driven the potential at either of the Junctions 8 0r 9 above the said critical potential of the grids 32 or 33. If the potential E is positive, the potential e at the junction 3 will be positive and, therefore, the junction 9 and the grid 33 of the tube 21 will be driven to a positive potential in the manner above described, and the tube 2'! will operate causing current from the alternating potential source 34 to discharge unidirectionally through the relay winding 36 causing the bell crank 39 to actuate the spring pressed pawl 4| and rotate the ratchet 42 and shaft 43 in a counterclockwise direction. There may be several discharges through the tube 21 before the relay armature is operated. The pawl spring returns the pawl and bell crank to their original positions. Energizing of the relay windin 36 also moves the armature 47 to close the grounded contact 49 and discharge the condenser C over the lead 48 thereby restoring the circuit to its initial condition in readiness to repeat the above described cycle. The discharge of the condenser C by operation of the armature 41 and the restoration of the grid 33 to its mean potential, causes stoppage of current flow through the valve 21 on the first subsequent reversal of current from the alternating current source 34.

A negative potential at E, on the other hand, drives the grid 32 of the valve 26 to a positive value permitting current from the source 34 to flow through the relay winding 38 to actuate the bell crank 44 and operate the spring pressed pawl 45 to rotate the associated ratchet 46 and shaft 43 in a clockwise direction. The winding 38 also operates armature 5| to close the grounded contact 53 thereby discharging the condenser C over the lead 48. This restores the potential of the grid 32 to its mean value and renders the valve 26 inoperative after the first subsequent reversal of current from the alternatin current source 34, and the circuit is again in condition for repetition of either cycle.

Inasmuch as the time required for the condenser C to reach a voltage which will cause grids 32 or 33 to deviate sufficiently from their mean potential to operate the respective valves 28 and 2'! is directly and substantially linearly proportional to the input voltage E, the shaft 43, or other movable member, will rotate in a direction and at a speed directly proportional to the value of the input voltage, except for small potentials which can be disregarded. Also, it should be noted that the rate of voltage increase on the condenser C is dependent on the value of the resistance R. By making this an adjustable resistance, as illustrated, the proportionality factor between the rate of rotation of the shaft 43 and the input voltage E may be varied at will. Furthermore, an additional control of the proportionality factor is obtained by the adjustable potentiometers 28 and 29 which determine the mean potential at junction 3 which is necessary to drive the grids to their operating potential.

.It is well known that a serious deficiency in direct current amplifiers has been a drift in their mean output potential due to various causes such as temperature and emissivity changes in the cathode, gas in the envelope of the valve and some other well known factors. The thermionic valve circuits herein shown mitigate this difficulty. For example, a change in cathode emissivity such as at the cathode l0 produces a change in space current to the anode of the respective valve connected to the source H, i. e., anode [5. This correspondingly affects the voltage across the associated cathode resistor l3, and, hence, the relationship of the cathode potential to that of the valve grids 4 and 18. This change in relative grid potentials causes an opposing change in current to the anode 2!] connected to the source 23. This stabilizes the anode current and also the mean output potential of the valve.

It will, therefore, be apparent that my improved amplifying apparatus is effective to produce two control potentials, the instantaneous values of which are positive and negative respectively, and which vary in response to variations in the potential to be amplified.

It should be understood that this invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of the invention.

I claim:

1. The combination in an amplifier circuit for producing a pair of control potentials of opposite polarity, of a pair of twin triode tubes, each tube including a cathode element, a pair of anodes, and a pair of grids, a high resistance in the oathode circuit, means for maintaining one anode of each tube at a substantially constant potential, a high resistance in circuit with the second anode of each tube, the grid associated with the constant potential anode in one tube being connected to the grid associated with the second anode in the other tube, and said grids being subject to a common impressed control potenial so that the potentials at said second anodes are related to said common control potential and are opposite in polarity with respect to each other.

2. The combination in an amplifier circuit of a source of variable potential, a pair of twin triode tubes, each tube including a common cathode element, a pair of anodes and a pair of grids, one grid of each pair being electrically connected to said source, a high impedance in the cathode circuit, means for maintaining one anode of each tube at a substantially constant potential, a high impedance in circuit with the second anode of each tube, the grid associated with the constant potential anode in one tube being connected to the grid associated with the second anode in the other tube, and output connections for said second anodes arranged so that the instantaneous potentials thereof respectively are of opposite polarity.

3. The combination in an amplifier circuit, of a source of variable potential, thermionic tube structure including two cathode elements, two pairs of anodes, and two pairs of grids, a high impedance in each cathode circuit, means for maintaining one anode of each pair at a substantially constant potential, a high impedance in circuit with the second anode of each pair, the grid associated with the constant potential anode in one pair being connected to the grid associated with the second anode in the other pair, said grids each being subject to the impressed variable potential, and output connections for one anode of each pair respectively arranged so that the instantaneous values thereof respectively are of opposite polarity.

RICHARD C. DEHMEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,208,254 Geohegan July 16, 1940 2,289,301 Barber July '7, 1942 2,376,392 Shepherd May 22, 1945 

